Objectives To validate the Visual Analog Scale (VAS) and Numerical Rating Scale (NRS) for measuring pain intensity in chronic oral mucosal diseases.Methods Secondary analyses of data including the VAS, NRS, demographic, clinical and quality-of-life outcomes at baseline and 4-month follow-up were retrieved from a clinical study of chronic oral mucosal diseases. Construct and criterion validity and responsiveness of the VAS and NRS were assessed through testing hypotheses based upon strength of Spearman's correlation coefficients.Results Data of 500 and 290 patients with chronic oral mucosal diseases were used for the assessment of validity and responsiveness, respectively. Moderate-to-high correlations between both pain scores and scores of clinical and quality-of-life outcomes were observed, supporting construct validity of the VAS and NRS. Their criterion validity was confirmed by significantly strong association between scores of both scales. Responsiveness of both scales was adequate based on moderate association between their change scores and global rating of change scale.Conclusion The present results provide evidence supporting validity and responsiveness of the VAS and NRS for pain intensity assessment in patients with chronic oral mucosal diseases. Future research examining other pain intensity domains and standardizing composite scores for pain intensity in this population is required.